The present invention relates to punching machines using a punching tool set which consists of at least one punch and one die which can be readily changed by machine controlled movement of a holder containing them.
There are various versions of such punching machines which use tool holders providing interchangeable tool sets, but they are rather expensive. Processing a piece normally made of sheet metal in a modern plant requires the use of many punching tool sets for many applications, one after another. As soon as one punching tool set has finished its action, it is exchanged for another, and then a third, etc. When the workpiece has been fully processed, the operator starts punching the next workpiece, again with the first punching tool set.
To make it possible to change punching tool sets quickly, each one is conveniently placed in a tool holder. Each punching tool set consists of at least one punch and one die corresponding to the cross section of the punch. Many times there is also included a stripper. The tool holders are constructed so that the complete punching tool set can be inserted in the tool storage assembly of the punching machine. From this position, they are automatically moved to the mounting position for the individual punching tool parts and locked in place for use. After punching with a tool set is finished, it and its holder are taken out of the tool feeder after the locking devices holding the tools in operative position are unlocked. This set is moved to a position where it does not interfere with the punching, but where it can still be reached again quickly and safely.
As will be appreciated, it would be relatively time consuming and thereby expensive to take the tools out of the holder and to replace them with a new set of tools. For this reason, each tool set is kept with its own holder on a shelf or in a storage device. The holder can be given a grip for manual changing; however, to do this, one must reach into the machine work area and this is not permitted around running machines for technical and safety reasons. Each manual tool change thus requires shutting down the punching machine.
It is also known how to transport the holder from a main storage area by means of a tool changing device to the punching tool feeder and from there back to the place of storage. In this case, it is especially advantageous if the changing device automatically exchanges the finished tool set and its holder. Generally, such machines utilize a comparatively expensive and space-intensive design. Moreover, they require a special control, which, especially with automatic punching machines, must be coordinated with their work program. Therefore, it is not unusual for the cost of the automatic tool changing feature alone to amount to one-fourth to one-third of the total cost of the punching machine.
It is an object of the present invention to provide a novel punching machine in which tool feeding to, and removal from, the tool mounting assembly is effected by the workpiece guidance system.
It is also an object to provide such a machine in which the tool sets carried by the workpiece guidance system may be readily exchanged.
Another object is to provide such a machine in which the tool sets on the guidance system may be exchanged with tool sets in an auxiliary storage area by automatic action of the machine.
A further object is to provide such an automatic tool changing punching machine which is relatively low cost but which is reliable in operation.